A wiring board mounted with a semiconductor device or a test wiring board used for an examination of a semiconductor wafer or an LSI chip includes a product in which a carbon fiber-reinforced plastic (CFRP) formed by impregnating a resin material into a carbon fiber is included in a core substrate. The core substrate including the CFRP has a low thermal expansion coefficient compared to, for example, a glass epoxy substrate. Accordingly, there is a case in which the CFRP is used in the core substrate of the wiring board so that the thermal expansion coefficient of the wiring board approximates to that of a mounted semiconductor device, thereby decreasing the heat stress between the wiring board and the semiconductor device.
A probe card is widely known as a test wiring board. A semiconductor wafer or an LSI chip is disposed on a surface of the probe card so that, for example, a high-temperature operation test or a low-temperature operation testis conducted. Using the CFRP for a core substrate of the probe card, the thermal expansion coefficient of the probe card may approximate to that of the semiconductor wafer or the LSI chip. As a result, for example, the positional difference between a conductive pad of the probe card and an electrode pin of the LSI chip may be avoided.
When wiring layers are laminated on both surfaces of the core substrate, a penetrating-through hole via is formed in many cases for an interlayer connection of the wiring layers. The penetrating-through hole via is formed by forming a through-hole that penetrates through a substrate in a thickness direction and, for example, depositing a plated film on an inner wall surface of the through-hole.
In a wiring board including a conductive core substrate such as the CFRP, there is a case in which the through-hole forming the penetrating-through hole via is manufactured to have a double structure in order to avoid an electrical short between the core substrate and the penetrating-through hole via. For example, there has been a penetrating-through hole via in which a through-hole for a lower hole and an inside through-hole formed inside thereof are formed on a substrate, and a gap between the through-holes having a double structure is filled with an insulation resin.
In the meantime, there is a case in which a conductive material is used for the core substrate and the core substrate is used as a specific power supply layer including a ground layer. In this case, the penetrating-through hole via does not need to be electrically insulated from the core substrate, and may be formed with a single structure.
However, since it is desired to form the through-hole for the lower hole in the penetrating-through hole via having the double structure, a cut cross-sectional area of the carbon fiber included in the core substrate may be different from that of the penetrating-through hole via having the single structure. Accordingly, when the conductive penetrating-through holes having the single structure and the double structure are formed together on the wiring board, the physical property, such as the thermal expansion coefficient or the elastic modulus is partially different, which causes a distortion by heat stress generated in the wiring board.
In this respect, it has been suggested that all of the penetrating-through hole vias formed on the wiring board has a double via structure to decrease the heat stress generated in the wiring layer. It has also been suggested that a micro via that connects conductive patterns of a core substrate side and a wiring layer side is formed on an insulation layer disposed between the conductive patterns of the core substrate side and the wiring layer side when the core substrate serving as the power supply layer is conductively connected with the penetrating-through hole via, thereby securing a connection through the micro via.
The followings are reference documents.                [Document 1] Japanese Laid-Open Patent Publication No. 2009-290124        [Document 2] Japanese National Patent Publication No. 2009-544153        [Document 3] Japanese Laid-Open Patent Publication No. 2009-99616        
However, there is a case where the insulation layer in the wiring layer is formed by hardening a prepreg obtained by impregnating an insulation resin into the fiber, such as a glass fiber. A laser may be used in order to form the micro via on the insulation layer. In this case, in order to cut the fiber included in the insulation layer, it is desired to increase the output of the laser. However, it is difficult to form a via hole that forms a micro via with a diameter of an opening or a depth of a perforation having a desired size so as to have an improved degree of precision. If the diameter of the opening or the depth of the perforation of the via hole is larger than a desired size, there is a concern that it is difficult to fill the via hole by a fill plating.
Since the surface of the insulation layer through which the via hole is perforated is covered by, for example, a copper foil in many cases, it is desired to remove the copper foil at a portion that forms the via hole by, for example, an etching process, as a pre-process of perforating the via hole. Accordingly, in a wiring board that includes a conductive core substrate and a plurality of penetrating-through hole vias, it may be considered that there is a room for improving the structure of a penetrating-through hole via (“a core connecting via”) disposed while being electrically connected with the core substrate.